I never actually claimed you were making this up, merely that the likelihood of your story being true was low. You inventing the story is only one possible reason why your story might be false. You could also simply be mistaken, have witnessed actions that looked much worse out of context (For example, maybe your friends did something to deserve their treatment, but didn't tell you because it would make them look bad) or some other reason I haven't thought of.

In addition, you ask why I care so much about lack of transparency when I can think of reasons why you'd want to keep information private. You gave none of this information in the original post, so if I were to come up with potential reasons why you might want to keep the information secret, I'd be rationalising.

With that in mind, evidence that your story is false:

• The prior probability of your claim is low. Not extremely low, but as when making any claim that isn't obvious, the "burden of proof" is upon you. (Naturally, I don't expect PROOF, hence the inverted commas, but you do need to provide sufficient evidence to overcome the initial low probability.)
• You claim to have references, yet don't provide them in the initial post or explain in the initial post why you won't publicly provide them. (Yes, you've given me an explanation now, which reduces the strength of this evidence, but does not eliminate it.)
• I have been unable to find any collaborating evidence for your story.
• The reaction on LessWrong, a site where the average member tends to be at least somewhat rational and probably at least as rational as myself, if not more so, is nearly universally negative.
• You've failed to provide verification. You claimed your story was easily verified, yet there's a conspicuous absence of any verification. Unlike your references, if your story is "easily verified", that means it's verifiable using public knowledge, and you haven't provided that knowledge. (If the story is verifiable by asking you, that does not count. You're asking us to verify the trustability of a source by asking that same source.)

Evidence that your story is true:

• You said it is. (Let's start with the obvious here.)
• Lack of discernable motivation for lying.
• Consquences if you're wrong, which you seem to care about. (Loss of karma/status in the group.)
• You've been around for a while.
• Decent chance people on LW would call you out on it if you were lying. (Thus making you less likely to try and fool people.)

In the end, the evidence for it being false is simply stronger. You've failed to overcome the burden of probability you've shouldered by making the claim. In order to overcome this burden, more evidence is required. Hence why I asked you to show the easy verification you claim exists, and post your references. If you have a good reason to not do the latter, at least do the former, and if you have a good reason not to do THAT as well, you'll just have to resign yourself to not being believed here.

The question is not precisely whether you are making this up, but whether your judgment of who is in the wrong is correct. I believe that a conference organizer offered to let someone attend for free, then midway through the conference, revoked that offer.

I am not certain whether the conference organizer or attendee is in the wrong. In short, your story has a perspective - and there is nothing wrong with that. But the tone of your essay is not internally consistent, or consistent with the message of the essay.

To put it differently, the organizer might say:

Running this conference is very expensive. I desire that everyone be able to attend for free, but I don't have the ability to do that. Instead, I offer free admittance to worthy folks that I select. It is very important to me that attendees at the conference participate fully. Thus, the people I admit for free are required to attend all the essential sessions. I'm sorry if I didn't communicate the attendance requirement or essential session list with sufficiently clarity that everyone understood my position, but that's the way things are. If you think you can run a conference on this topic better than I, you are welcome to set up your own, with your own rules.

Such an organizer might be legally liable for some costs (on a breach of contract or other legal theory). Such organizer might be morally wrong, or a very stiff necked jerk. But such a person would not be delusional or mentally ill.